Across the U.S., nearly 8,000 facilities in nine industry sectors – including power plants, refineries, chemicals and waste – reported what equaled 3.3 billion metric tons of carbon-dioxide emissions. California accounted for about a third of that, with 491 facilities reporting more than 1 billion metric tons.

L.A. County, for its part, saw 80 facilities report more than 26 million metric tons of carbon dioxide equivalents.

Responding to the World Health Organization's decision to rate diesel fumes as a Group 1 carcinogen last June, environmental experts told OnCentral that Los Angeles is "dominated by diesel vehicles." Dense South L.A., in particular, is cordoned off by the 10, 105 and 710 freeways, with the 110 going straight through its heart. Those routes, along with the Alameda Corridor, make air quality an issue.

"The Alameda Corridor is where a lot of locomotives that are leaving L.A. with goods for the rest of the country travel," Andrea Hricko, a professor of preventive medicine at USC, said in June. "You've got people in South L.A. who are exposed to that exhaust."

The EPA had 2011 statistics for several facilities in the South L.A. area, including the following four:

The EPA did note that power plants "remain the largest stationary source of greenhouse gas emissions," but that 2011 emissions were 4.6 percent lower than 2010's numbers. That, said the agency, reflects "an ongoing increase in power generation from natural gas and renewable sources."